The present invention relates to a measuring tool and more particularly to a measuring tool which provides measurement of a rotor blade cuff without rotor blade disassembly.
A rotor blade spar is a primary structural element of a helicopter main rotor blade assembly inasmuch as its primary function is to transfer combined flapwise, edgewise, torsional and centrifugal loads to/from a central torque drive hub member. Typically, a leading edge and trailing edge assembly envelope the spar to yield a desired airfoil contour. The spar extends along the length of the rotor blade and mounts at its inboard end to a cuff assembly that facilitates mounting of the rotor blade to a rotor hub assembly. The cuffs are typically manufactured as one-piece members which are mechanically fastened and bonded to the blade spar and blade skins.
The blade cuffs are flight safety components which must be within predefined dimensional variation tolerances to ensure flight integrity. Oftentimes, the blade cuffs may become damaged through normal flight operations. Some dimensional variation is permissible within predetermined limits, and some damage may be repaired through accurate measurement of the damage depth, material removal, blend direction, and surface finish to maintain the strength integrity of the blade cuff.
When damage beyond predetermined limits occurs to the blade cuff, the blade cuff must be removed from the main rotor blade assembly to repair the blade cuff. Blade cuffs are typically mechanically fastened and bonded to the rotor blade and removal of the blade cuff is a relatively expensive and laborious procedure. Removing the blade cuff may also result in disbonding of the blade root laminate which may increase future disbonding of the rotor blade.
Disadvantageously, blade cuff damage beyond predetermined limits may be relatively difficult to identify which may result in disassembly of an acceptable blade cuff from a flight acceptable rotor blade assembly.
Accordingly, it is desirable to provide accurate in-situ measurement of a rotor blade cuff without necessitating disassembly of the blade cuff from the rotor blade assembly.